Analysis of the helical plate for bone fracture fixation.

The improvements in oblique fracture fixation by means of the hemi-helical plate (HHP) to provide the bone-plate-screw assembly with enhanced holding capacity are discussed. The HHP is designed to provide stable fixation for helical cracks caused by torsional loading, such that the bone interfaces at the crack are brought into apposition and compressive strains are applied at the cracked interfaces. The HHP wraps around the bone, and hence is also suited for fixation of comminuted fractures. This is because, instead of employing multiple screws across the cracks, the HHP holds the bone fragments together. First, we illustrate through experiments the special capabilities of the HHP with respect to its fracture-holding capability, in comparison with straight-plate fixation with different screw orientations (convergent, divergent, alternately convergent and divergent, and perpendicular). Second, the finite-element (FE) analysis of the HHP is described, to elucidate the efficacy of fracture-gap movement and closure, and the flexibility of the fixation under compressive, bending moment and torsional loads.